Adjustable Gas Block

ABSTRACT

An adjustable gas block designed to interface with the gas-operating system of an auto-loading firearm. This design provides continuously adjustable gas flow, from fully closed to fully open, in small, discrete, uniform, and fully-repeatable increments. 
     The design works by means of a click adjustment valve screw which has a number of grooves that are engaged by a spring-loaded detent. As the screw is turned in or out, either by a tool or by an integrated finger-adjustable knob or handle, the clicks of the detent provide both audible and tactile feedback to the user. This allows a user to optimize the operation of a firearm by responding to variations in ammunition loading, bullet weight, atmospheric temperature, cartridge caliber, and for the installation/removal of a silencer, each of which changes the volume and pressure characteristics of the gas-operating system.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of provisional patent application No. 61/550,569, filed 2011 Oct. 24 by the present inventor.

FEDERALLY SPONSORED RESEARCH

Not Applicable.

SEQUENCE LISTING

Not Applicable.

BACKGROUND-FIELD OF INVENTION

This invention relates to gas-operated auto-loading firearms, and specifically to user-adjustable gas blocks for such firearms.

BACKGROUND-PRIOR ART

A gas block for an auto-loading firearm is a device that is placed usually on the barrel of an auto-loading firearm, and used as a means to tap, collect, restrict, and direct the flow of propellant gas from the firearm's barrel into the auto-loading mechanism so as to provide the necessary energy to operate the auto-loading firearm. Adjustable gas blocks have been used on military auto-loading firearms for decades, as seen in such firearms as: the Soviet SVD; Yugoslavia's models 70, 76, and 95; the Belgian FAL; and recent Belgian SCAR rifles. In addition, some commercially sold rifles, such as the AR10 SASS and variants like the JP Enterprises LRT 07, also use some form of adjustable gas block technology.

Early adjustable gas blocks were used to help minimize wear of the firearm by providing only enough gas to properly operate the firearm's auto-loading mechanism. Another application was to adapt the firearm to fire rifle-mounted grenades, with the use of a special cartridge. Some early adjustable gas blocks, such as the Yugoslav design, were also used to compensate for different ammunition or extreme fouling build-up under battlefield conditions, when complete cleaning was not practical. These early designs typically had only two or three settings, and were usually adjusted by movement of a drum valve with different sized ports drilled in it, which were aligned with a corresponding port that communicated with the auto-loading mechanism. By turning the drum so as to align a smaller or larger port, the amount of propellant gas allowed into the operating system could be regulated (reduced or increased) in a limited way. More recent variations of the drum-type valve have been used to compensate for the installation or removal of a silencer.

Historically, there are three basic adjustable gas block designs:

-   -   1. The drum valve version. In this design, the drum valve,         itself, resides either in or in front of the gas tube on an         M16/AR15/AR10/M4 type firearm; or in front of the gas cylinder,         in the case of a piston-driven mechanism. This design is         exemplified by the AR10 SASS and Yugoslav designs cited above,         and more recently by the Noveske patent (U.S. Pat. No. 7,856,917         B2).     -   2. The set screw adjustable version. This design uses a common         socket head set screw as a valve screw that can be continuously         adjusted in and out to occlude, to a varying amount, the         passageway between the barrel and the gas tube or gas cylinder.         This design has been adapted to M16/AR15/AR10/M4 type firearms,         and is sold by vendors such as Brownells, Inc. of Montezuma,         Iowa.     -   3. The vent cover version. This design is exemplified by the         Belgian FAL, and uses a nut, placed on the outside of a threaded         gas cylinder, to cover or uncover more or less of the area of a         hole drilled through the cylinder, thus venting more or less gas         to the atmosphere.

DISADVANTAGES OF THE PRIOR ART

The drum valve design has three inherent disadvantages. First is the very limited range of adjustment settings, typically two or three. These settings are usually comprised of fully closed, fully open, and one setting in between (typically engineered for a specific purpose). Second is the large surface areas of the mating parts (comprising the drum valve itself and the cylinder inside which it rotates). These surfaces are subject to buildup of carbon fouling from the propellant gas. After as few as 200 rounds have been fired, the valve can be rendered immovable without the use of large, and seldom field-available, tools. Third is the fixed-size orifices of the drum. These predetermined sizes are not adaptable to such field variables as: wear of the mating parts; wear of the rest of the firearm's operating system; the sometimes wide variation in working pressure of the ammunition in use; or other unforeseen field variables.

The prior art valve screw design, making use of a common socket head set screw to occlude the port between the barrel and the gas tube on M16/AR15/AR10/M4 type firearms, has two significant disadvantages. First is that nothing holds the screw in adjustment. An expedient remedy for this shortcoming is to apply a commercial thread-locking compound, such as Loctite, to the adjustment screw's threads. However, this action creates another problem: with the screw head locked in place, the extremely small hex wrench, used for adjustment, only serves to strip out the hex socket in the screw's head, thus rendering the screw removable only after extensive disassembly of the firearm. The second disadvantage of this design is that the adjustments are not precisely repeatable. A user may effectively adjust the valve for one set of circumstances, change it for another set of circumstances, but be unable, without long experimentation and expenditure of ammunition, to return to the first setting.

The vent cover design, as used on the Belgian FAL, has two major disadvantages. First, by directly venting excess gas to the atmosphere, this design negates the use of a silencer; a vented blast and flash makes a silencer ineffective. Second, this design is only usable in piston-driven auto-loading firearms. Direct impingement systems, as are used on M16/AR15/AR10/M4 type firearms, have no external gas cylinder on which such a design could be used.

ADVANTAGES OF THE INVENTION OVER PRIOR ART

The present invention uses a continuously adjustable valve screw. Not limited to two or three settings, the valve screw can be easily adjusted to any setting between fully open and fully closed, with a number of discrete and fully repeatable adjustment settings in-between. This means the firearm's gas-operated auto-loading mechanism can now be quickly adjusted for differences in ammunition loading, bullet weight, atmospheric temperature, cartridge caliber, and for the installation/removal of a silencer. This gas block adjustment mechanism does not vent excess gas, or its consequent noise and flash, to the atmosphere. Both are undesirable characteristics when a firearm is sound-suppressed.

The present invention uses a click adjustment valve screw offering precisely repeatable and recordable settings, or clicks. Adjustments can be precisely repeated by simply counting clicks down from fully open or up from fully closed. This process is very much like adjusting sight settings, something with which most users are already familiar.

Embodiments of the present invention use a detent mechanism to engage grooves in a click adjustment valve screw that positively retains the user's adjustment setting, eliminating the need for a thread-locking compound.

Embodiments of the present invention use a click adjustment valve screw with a larger socket head, enabling the use of a larger size wrench, or, in another embodiment, a finger-manipulable knob, neither of which are prone to stripping out. Incorporating a coin slot in the finger-manipulable knob, to facilitate manual adjustment, is yet another embodiment of the present invention.

Embodiments of the present invention can be adjusted by using a larger size wrench or finger-manipulable knob via an access port provided in the side of an extended fore-end. Alternately, embodiments of the present invention could have the adjustment apparatus oriented in such a way as to be accessed from the open front end of an extended fore-end. The installation of an extended fore-end is increasingly popular on carbines and other short-barreled rifles, and serves to protect users' hands from being burnt by a hot barrel.

In addition, the present invention's precisely and finely adjustable increments have led to the discovery of several unforeseen advantages. 1.) The click adjustment valve screw can now be used as a barrel tuner, and highly accomplished marksmen can use it to enhance the inherent accuracy of their firearm. 2.) The gas-operating system can now be finely tuned to the installation of a silencer and its resultant increase in back pressure and fouling, compensating to the point where the additional fouling caused by this back pressure is all but eliminated. This can make a positive improvement in field reliability, and serve to reduce maintenance requirements of a given firearm. 3.) It has been found that when a click adjustment valve screw is adjusted to its optimal setting—of two clicks more open than are required to just lock back the bolt on an empty magazine—the firearm's cyclic rate is reduced during fully automatic fire. This makes the firearm much more user-controllable during fully automatic fire. 4.) The inevitable carbon buildup, in the threads of a click adjustment valve screw, does not jam or otherwise render the adjustment mechanism unusable. To the contrary, it actually seems to act as a lubricant.

SUMMARY

Provided is an adjustable gas block for a gas-operated auto-loading firearm, also referred to herein as an improved adjustable gas block. The improved adjustable gas block has a main housing manufactured of metal or other suitable material, longitudinal bores for the firearm's barrel and gas tube or cylinder, and a gas transfer port connecting those two bores. The gas transfer port is transversely intersected by a click adjustment valve screw which incorporates a spring-driven detent mechanism to hold the click adjustment valve screw in place when adjusted to any position from fully open to fully closed. Both the fully open position and the fully closed position are provided with positive mechanical stops. By counting detent “clicks” from either fully open or fully closed, a user can easily return the click adjustment valve screw to a pre-determined setting, and compensate for field variables such as: ammunition loading, bullet weight, atmospheric temperature, cartridge caliber, and for the installation/removal of a silencer. Adjustments can be made in precise, uniform, repeatable clicks, each of which accounts for a small incremental change in the amount of propellant gas allowed into a host firearm's gas-operating system, and is thus adaptable to a wide variety of field variables, as well as to many types of gas-operated auto-loading firearms. Adjustments may be made to a click adjustment valve screw either by use of a separate tool or a finger-manipulable knob, attached or integral, which may have a slot fitted for a coin or screwdriver.

DRAWINGS Figures

FIG. 1 is a side view of an auto-loading firearm with an embodiment of an improved adjustable gas block, a silencer, and a standard length fore-end.

FIG. 2 is a side view of an auto-loading firearm with an embodiment of an improved adjustable gas block, a silencer, and an extended fore-end.

FIG. 3 is a front view of a firearm barrel and fore-end (same firearm as seen in FIG. 2) sectioned vertically through the firearm's barrel at the intersection of the barrel and the front of an embodiment of an improved adjustable gas block. This view shows an adjustment tool inserted through an access port in an extended fore-end, and into the hex socket head of a click adjustment valve screw.

FIG. 4 is another front view of a firearm barrel and fore-end (same firearm as seen in FIG. 2) sectioned vertically through the firearm's barrel at the intersection of the barrel and the front of an embodiment of an improved adjustable gas block. This view shows a finger-manipulable knob, either attached separately or manufactured integrally with a click adjustment valve screw, protruding through an access port in an extended fore-end.

FIG. 5 is an exploded view showing an embodiment of an improved adjustable gas block disassembled from a firearm barrel and gas tube.

FIG. 6 shows an embodiment of an improved adjustable gas block (same as seen in FIG. 5) in the installed position on a firearm barrel and gas tube. The area of the sectional cutaway view of FIG. 18 is circled.

FIG. 7 illustrates a portion of a firearm barrel and gas tube with an embodiment of an improved adjustable gas block installed, and with a tool inserted into the head of a click adjustment valve screw. The locations of sectional FIGS. 9, 10, and 17 are noted.

FIG. 8 is a perspective drawing oriented from the right rear of an embodiment of an improved adjustable gas block, and which depicts the location of the sectional views in FIGS. 11, 12, 13, 14, and 15.

FIGS. 9 through 15 are sectional views showing the operation of a click adjustment valve screw and detent mechanism assembly, and the physical relationships of the various components in detail.

FIG. 16 is a gas flow diagram depicting an embodiment of an improved adjustable gas block regulating gas flow in the gas-operating system of an auto-loading firearm equipped with a silencer.

FIG. 17 is a vertical section of an embodiment of an improved adjustable gas block mounted on a firearm barrel, and showing the alignment relationship of the gas port in the barrel, the gas transfer port in an embodiment of an improved adjustable gas block, and the gas inlet port in the firearm's gas tube.

FIG. 18 is a sectional cutaway view of the area circled in FIG. 6 showing the detail of gas flow from a firearm barrel, through a click adjustment valve screw with its associated detent mechanism assembly, and into a firearm's gas tube.

FIGS. 19 through 22 illustrate some possible embodiments of an improved adjustable gas block's click adjustment valve screw.

FIG. 23 is an exploded isometric view of a slightly different embodiment of an improved adjustable gas block.

FIGS. 24 and 25 illustrate an embodiment of an improved adjustable gas block incorporated into a front sight assembly.

FIG. 26 illustrates an embodiment of an improved adjustable gas block with an integral accessory rail.

DRAWING Reference Numerals

-   -   1 Complete assembly of an embodiment of an improved adjustable         gas block     -   2 Main housing of an embodiment of an improved adjustable gas         block (which can be of different shapes to serve specific         functions)     -   4 Detent mechanism assembly     -   5 Detent element         -   5 a Detent ball         -   5 b Detent pin     -   6 Detent spring     -   7 Detent mechanism retention screw     -   8 Retention screw for click adjustment valve screw     -   10 Click adjustment valve screw     -   12 Gas flow adjustment end         -   12 a Shaped end         -   12 b Squared end     -   14 Valve screw drive method         -   14 a Hex socket head         -   14 b Finger-manipulable knob     -   16 Threads on click adjustment valve screw     -   18 Detent grooves in click adjustment valve screw     -   20 Extension, which may be threaded or unthreaded, of the hole         for the click adjustment valve screw in main housing     -   21 Threaded hole in main housing for click adjustment valve         screw     -   22 Countersink in main housing for head of valve screw     -   23 Through hole in main housing for detent element and spring     -   24 Bore in main housing for gas tube     -   26 Longitudinal bore in main housing for barrel     -   28 Blind hole in main housing for detent element and spring     -   29 Gas transfer port in main housing, through which propellant         gas moves from barrel gas port to factory gas tube inlet port     -   32 Common hex key tool for adjusting click adjustment valve         screw     -   34 Apparatus to secure improved adjustable gas block to barrel         of host firearm         -   34 a Common socket head set screws         -   34 b Clamp mechanism     -   40 M16/AR15/AR10/M4 type firearm     -   42 Firearm receiver (combined upper and lower firearm receiver)     -   44 Firearm gas tube as supplied by factory     -   46 Firearm barrel     -   48 Standard length fore-end     -   50 Extended length fore-end     -   52 Access port in extended fore-end to enable adjustment of         click adjustment valve screw     -   54 Common roll pin used to secure gas tube to gas block     -   58 Silencer of any brand or type     -   62 Gas port in factory firearm barrel     -   64 Firearm barrel bore     -   66 Factory gas tube inlet port     -   68 Internal bore of factory gas tube

DETAILED DESCRIPTION OF THE INVENTION

An auto-loading firearm's gas-operating system is one which utilizes a portion of the firearm cartridge's propellant gas as the energy source to operate the firearm's auto-loading mechanism. The illustrated embodiments of the invention are designed to provide users of gas-operated auto-loading firearms with a means of precisely and repeatably adjusting the amount of gas which is allowed to pass from the barrel of a host firearm into its gas-operating system, thus providing the ability to optimize the operation of a firearm by compensating for variations in ammunition loading, bullet weight, atmospheric temperature, cartridge caliber, and for the installation/removal of a silencer. The term “gas-operated auto-loading firearm” as used in this document includes, but is not limited to, direct impingement systems such as M16/AR15/AR10/M4 type of firearms, as well as firearms that utilize a piston and cylinder in their gas-operating system. Please note that while the illustrated embodiments depict installation on an M16/AR15/AR10/M4 type firearm, the essential features of the herein described invention are not limited to these types of firearms or gas-operating systems.

Turning to the drawings, in which like reference numerals indicate corresponding elements throughout the several views, attention is directed to FIGS. 1, 2, 3, and 4, which illustrate an embodiment of an improved adjustable gas block 1 mounted on an M16/AR15/AR10/M4 type of firearm 40. FIG. 1 shows an M16/AR15/AR10/M4 type auto-loading firearm 40 with its upper and lower receiver 42, an embodiment of an improved adjustable gas block 1, a standard length fore-end 48, a gas tube 44, and rifle barrel 46. Also depicted is a generic silencer 58. FIG. 2 illustrates the same rifle as seen in FIG. 1, but now with an extended fore-end 50 replacing the standard length fore-end 48. The extended fore-end 50, which in this case almost completely covers an embodiment of an installed improved adjustable gas block 1, has an opening or access port 52 through which the hex socket head 14 a of a click adjustment valve screw 10 can be adjusted with a common hex key tool 32, as shown in FIG. 3. A finger-manipulable knob 14 b, depicted in FIG. 4 and shown by itself in FIGS. 21 and 22, is a possible alternative embodiment of a click adjustment valve screw 10, and enables adjustment of gas flow without a separate hex key tool 32.

An embodiment of an improved adjustable gas block 1 is intended as a replacement for a standard fixed-port gas block, well known in the prior art, and is for use on an auto-loading firearm 40. In this embodiment, an improved adjustable gas block 1 is designed to utilize the standard gas tube 44 and attachment roll pin 54 used in M16/AR15/AR10/M4 type firearms. This is shown in the exploded view in FIG. 5, and the assembled views in FIGS. 6 and 7. These parts and their method of attachment are well-known in the prior art and will not be discussed further, except to note that another embodiment of the invention could be used on other types of firearms, such as those with a gas system which utilizes a piston and cylinder.

FIGS. 8 through 18 illustrate an embodiment of an improved adjustable gas block 1, which consists of: a main housing 2, click adjustment valve screw 10 with detent grooves 18, detent element 5, and detent spring 6. The detent element 5 (which could be either a ball 5 a or a pin 5 b) and detent spring 6 comprise the detent mechanism assembly 4, and reside in a blind hole 28 provided in the main housing 2. The hole in the main housing 2 for the detent mechanism assembly 4 could be either a blind hole 28, as depicted in FIG. 11, or a through hole 23, as shown in an alternative embodiment in FIG. 23. Additionally, FIG. 23 shows a detent mechanism assembly 4 and detent mechanism retention screw 7, which retains the detent mechanism assembly 4 in the housing 2, and maintains spring tension on the detent element 5 b. The main housing 2 should be manufactured of a suitable material to withstand the pressure imposed by the propellant gas introduced from the factory gas port 62 in the firearm barrel 46. To this end, the main housing 2 could be machined or cast of metal or formed using powdered metal technology or manufactured by some other means using a similar strength material.

Turning now to FIGS. 9, 10, and 11, we can see that a mechanism has been provided to limit the travel of a click adjustment valve screw 10 when it is in the open position, and prevent its inadvertent removal during use. In this embodiment, a retention screw 8 for click adjustment valve screw 10 is positioned so as to have its head overhang the head of the click adjustment valve screw 10 sufficiently to prevent the click adjustment valve screw 10 from being removed during operation. It also provides a positive stop to the click adjustment valve screw's 10 travel when in the fully open position. Vertical sections FIGS. 9 and 10 show that the main housing 2 has a countersink 22 sufficiently deep so as to accommodate the full travel length of the head of a click adjustment valve screw 10. The bottom of the countersink 22 serves as a positive stop to the fully closed position of a click adjustment valve screw 10 (fully closed position seen in FIG. 9). Conversely, the retention screw 8 acts as a positive stop to a click adjustment valve screw's 10 fully open position (fully open position seen in FIG. 10).

Four versions of a click adjustment valve screw 10 are shown in FIGS. 19, 20, 21, and 22. Turning first to FIG. 19, we see a click adjustment valve screw 10 with a gas flow adjustment end 12 having a shaped end 12 a, and incorporating a click adjustment valve screw drive method 14 configured with a hex socket head 14 a. A common hex key tool 32 (seen in FIGS. 3 and 7) is used as a wrench to turn a click adjustment valve screw 10 in and out. In addition, axial grooves 18, the full length of a click adjustment valve screw's 10 head, engage the detent element 5 of the detent mechanism assembly 4. (This relationship is illustrated in FIG. 11.) Turning now to FIG. 21, we again see a shaped end 12 a of a click adjustment valve screw 10, but here the click adjustment valve screw drive method 14 is a finger-manipulable knob 14 b. This embodiment (also seen in FIG. 4.) allows click adjustment valve screw 10 adjustment from outside an extended fore-end 50 without the need for a separate tool. Continuing with the description of four click adjustment valve screw 10 versions, FIGS. 20 and 22 illustrate embodiments of the two click adjustment valve screw drive methods 14 introduced above, but now with a gas flow adjustment end 12 having a squared end 12 b. It will also be noted that the click adjustment valve screw's 10 outside threads 16 engage corresponding threads in the threaded hole 21 of the housing 2 (illustrated in FIGS. 9 through 15). All versions of a click adjustment valve screw 10 have axial grooves 18 to engage the detent element 5. It is to be expressly understood that these embodiments of a click adjustment valve screw 10 are presented by way of example, and are not intended to limit possible physical configurations of a click adjustment valve screw 10.

A click adjustment valve screw 10 seals off the flow of gas when in the fully closed position. FIG. 11 shows that a shaped end 12 a of a click adjustment valve screw 10 could be manufactured to correspond to the curved profile of the inside of the gas transfer port 29. These corresponding contours serve to create an effective seal when a click adjustment valve screw 10 is turned to the fully closed position. Other effective sealing strategies are possible. Two possible alternate embodiments of a threaded hole 21 with an extension 20 continuing through the opposite side of the gas transfer port 29 are shown in FIGS. 14 and 15. In FIG. 14 an embodiment of a click adjustment valve screw 10 with a squared gas flow adjustment end 12 b is shown. This embodiment of a click adjustment valve screw 10 would completely traverse the gas transfer port 29 and extend into a threaded extension 20 of a threaded hole 21. FIG. 15 depicts a shaped gas flow adjustment end 12 a which would seat into an unthreaded extension 20 of a threaded hole 21. In this illustration of this embodiment, the hole extension is manufactured to provide a seating area for a shaped gas flow adjustment end 12 a.

Irrespective of design version, an embodiment of a click adjustment valve screw 10 can be rotated a number of turns from fully open to fully closed. When fully open, it provides the amount of gas to the firearm's operating system that a normal factory-supplied fixed-port gas block would allow. When fully closed, it provides no gas at all to the operating system, and the auto-loading mechanism of the firearm will not function. In the fully closed position, the firearm can still be manually cycled. (FIG. 10 shows a fully open position while FIG. 9 shows a fully closed position.) Between fully open and fully closed, ten or more adjustment positions can be provided, depending on the number of detent grooves 18 manufactured into a click adjustment valve screw 10, and the pitch of the screw's threads 16. As a click adjustment valve screw 10 is rotated open or closed, the detent element 5 clicks from groove to groove in the detent grooves 18, thus providing tactile and audible feedback to the user as to the position of a click adjustment valve screw 10. In this way, by counting clicks down from fully open or up from fully closed, a user can precisely return an embodiment of an improved adjustable gas block to a pre-determined setting, which is based on such factors as variations in ammunition loading, bullet weight, atmospheric temperature, cartridge caliber, and the installation/removal of a silencer. Once an optimum position of adjustment, based on such variables as listed above, is determined, a detent element 5, held by the detent spring 6 against and into one of the detent grooves 18, prevents the movement of a click adjustment valve screw 10 from its selected setting, until such time as a user deliberately changes the setting. (This relationship is clearly seen in FIG. 11.) Additionally, the sectional and cutaway views shown in FIGS. 9, 10, 11, 12, 13, 14, 15, and 18 provide several illustrations, from various different viewpoints, of a click adjustment valve screw 10 and detent mechanism assembly 4 in an embodiment of an improved adjustable gas block 1.

The concept of gas passageway interconnectivity is described in the following paragraph and depicted in several figures. First, as seen in the exploded view of FIG. 5, a bore 24 is provided in a main housing 2 to receive the gas tube 44, which is connected to an improved adjustable gas block with a common roll pin 54. (These components are seen assembled in FIG. 6.) Turning now to FIG. 17 and FIG. 18, we are shown a vertical sectional view (FIG. 17) and a cutaway view (FIG. 18) of this embodiment of an improved adjustable gas block 1 mounted on a firearm barrel 46 with gas tube 44 installed. FIG. 17 illustrates the assembled relationships of the gas ports in the various parts, wherein one can clearly see the gas transit interconnections: from the barrel bore 64, through the barrel gas port 62, continuing through an improved adjustable gas block's gas transfer port 29, then via the gas tube inlet port 66 of a factory gas tube 44 and into the internal bore of the factory gas tube 68, and finally into the gas-operating system of a firearm 40. FIG. 18 clearly shows a click adjustment valve screw 10 in position to regulate the amount of propellant gas allowed to flow from the bore 64 of the firearm barrel 46, through the factory barrel gas port 62, subsequently through the gas transfer port 29 in the main housing 2, proceeding through the gas tube inlet port 66 in the factory gas tube 44, and finally down the internal bore 68 of the factory gas tube 44, and hence, as seen in FIG. 16, into the factory-supplied components within the receiver 42 of a host firearm 40.

The concept of gas flow regulation is discussed here and diagrammatically illustrated in FIG. 16. Gas flow from the barrel 46 of a gas-operated auto-loading firearm 40 to its gas-operating system is conventionally set at the factory, and is based on the length of the barrel 46 present on the host firearm 40 and the distance of the barrel gas port 62 from the receiver 42 of said firearm 40. However, if a silencer 58 is installed on the firearm 40, as depicted in FIG. 16, gas exiting the muzzle is severely restricted, increasing the overall pressure, and duration of that pressure, within the host firearm's gas-operating system. This “back pressure” forces more gas than is optimal into the gas-operating system of the host firearm 40, creating an “over-gassed” condition. FIG. 16 also depicts a means of compensation for this condition: when a click adjustment valve screw 10, of an embodiment of an improved adjustable gas block 1, is turned a number of its small, discrete, uniform increments, or clicks, toward the closed position, the gas transfer port 29 becomes progressively occluded and gas flow into the gas tube 44 is restricted. An optimal setting can be found that facilitates correct operation of the host firearm's gas-operating system with a silencer 58 installed. The adjustment position is held firmly in place by the detent assembly 4. Additionally, with correct operation of the host firearm's gas-operating system in mind, a user could determine other optimal settings to compensate for differences in ammunition loading, bullet weight, atmospheric temperature, and cartridge caliber.

In FIG. 16 we also see illustrated a different possible physical orientation of a click adjustment valve screw 10 and its detent mechanism assembly 4. In this illustration a click adjustment valve screw 10 is accessible from the front, or muzzle end, of a firearm 40.

Additionally, a click adjustment valve screw 10 in an improved adjustable gas block 1 can also be employed to compensate for the conversion of a host firearm to a completely different caliber than that for which it was originally designed.

It is useful to note at this point that when an embodiment of an improved adjustable gas block 1 is in the fully open position, the factory amount of gas is allowed to pass through the barrel gas port 62 and into the gas tube 44 via the gas tube inlet port 66 in said gas tube.

The longitudinal bore 26 (shown in FIGS. 14 and 15) in the main housing 2 for a firearm barrel 46 in an embodiment of an improved adjustable gas block 1 must be accurately manufactured to fit snugly around the diameter of the barrel 46. Turning again to FIG. 17, the mounting position of an embodiment of an improved adjustable gas block 1 is selected so that the gas port 62 on a barrel 46 is positioned under the gas transfer port 29 located on the inside of the main housing 2. An embodiment of an improved adjustable gas block 1 is then secured to the barrel 46 using an attachment apparatus 34. By way of example, the attachment apparatus could be set screws 34 a, as seen in FIG. 23, or a clamp mechanism 34 b, as seen in FIG. 26 or one of several other methods not illustrated herein but well-known in the prior art.

FIGS. 24 and 25 illustrate yet another embodiment of an improved adjustable gas block 1, this embodiment incorporated into a front sight. FIG. 26 is an illustration of yet another possible embodiment of an improved adjustable gas block, this embodiment having an integral top accessory rail. Please bear in mind that these illustrated embodiments should in no way be held to limit the possible scope of the invention.

Upon installation of an improved adjustable gas block 1 on a host firearm 40, a user could follow this procedure to find the optimal initial setting for an improved adjustable gas block's 1 click adjustment valve screw 10:

-   -   1. Turn the click adjustment valve screw 10 all the way open         until it touches the retention screw 8. The improved adjustable         gas block 1 now delivers as much gas to the gas-operating system         as the factory barrel gas port 62 will allow.     -   2. Load one cartridge only in the magazine. Fire the single         round and confirm that the bolt locks back on the empty         magazine. If it does not, check installation and port alignment.     -   3. If it does, turn the click adjustment valve screw 10 one         click closed and repeat step 2. Repeat this procedure until the         bolt does not lock back, then open the click adjustment valve         screw 10 two clicks and confirm the firearm's functionality. If         any stoppages are detected, open the click adjustment valve         screw 10 one more click and re-check function. Count the number         of clicks required to open the click adjustment valve screw 10         until it touches the retention screw 8. Record the setting. (A         user could choose to count up from fully closed, as well as down         from fully open.)

By recording settings for previously-tested conditions or installed equipment, a user could quickly optimize a firearm's performance in response to changes in field conditions or equipment by adjusting a click adjustment valve screw 10 to a pre-determined setting. If, for example, a silencer is installed, a click adjustment valve screw 10 would be turned a predetermined number of clicks toward the closed position to compensate for the increased back pressure within the firearm's gas-operating system. Tactile and audible feedback indicates the screw's position, with each click opening/closing the firearm's gas port in small, uniform, discrete, and repeatable increments. By counting clicks down from fully open or up from fully closed, an embodiment of an improved adjustable gas block can be precisely returned to a given setting—even in the dark.

CONCLUSIONS, RAMIFICATIONS, AND SCOPE

Accordingly, the reader will see that an improved adjustable gas block as described herein is a novel and useful invention with widespread application in gas-operated auto-loading firearms. 

I claim:
 1. An improved adjustable gas block for a gas-operated auto-loading firearm, the firearm having a receiver with a forward end, a barrel with a gas port, and a gas tube with a gas inlet port, the barrel and gas tube joined to the receiver forward end, and the improved adjustable gas block comprising: a) a gas block housing manufactured of a suitable material with an apparatus to secure the gas block to the barrel, the gas block housing having a longitudinal bore extending through the housing to receive the firearm barrel, and having a second bore parallel to the first bore and extending a predetermined distance and adapted to receive the firearm's gas tube, b) the gas block housing also including a gas transfer port, further defined as aligned with both the barrel gas port and the gas tube inlet port, which when unobstructed permits the flow of propellant gas from the barrel gas port through the gas transfer port into the gas tube inlet port and thence to the firearm receiver, so as to operate the firearm's auto-loading mechanism, c) the gas transfer port being transversely intersected by a click adjustment valve screw with a distance of travel sufficient to render the gas transfer port either entirely open to the unhindered passage of propellant gas or entirely closed so as to completely prevent the flow of gas, d) the click adjustment valve screw further, having an area larger in diameter than the threaded body, and having evenly spaced grooves manufactured in said area parallel with the axis of the screw shank, said grooves being engaged by a spring-driven detent mechanism, being able thereby to be adjusted, either by use of a tool or a finger-manipulable knob, so as to be in a number of discrete positions between fully open and fully closed, the detent mechanism holding the click adjustment valve screw in a precise, repeatable setting.
 2. The adjustable gas block of claim 1 embodied in a front sight.
 3. The adjustable gas block of claim 1 embodied in a gas block with an integral accessory rail.
 4. The adjustable gas block of claim 1 further comprising a click adjustment valve screw with a finger-manipulable knob or handle.
 5. The adjustable gas block of claim 1 further comprising a click adjustment valve screw with a finger-manipulable knob or handle which also has a slot fitted for a coin or screwdriver.
 6. The adjustable gas block of claim 1 wherein the click adjustment valve screw has a shaped end.
 7. The adjustable gas block of claim 1 wherein the click adjustment valve screw has a squared end.
 8. The adjustable gas block of claim 1 wherein the detent element is spherical in shape.
 9. The adjustable gas block of claim 1 wherein the detent element is a pin.
 10. The adjustable gas block of claim 1 wherein a mechanism is provided to prevent the click adjustment valve screw from being inadvertently removed during use, and said mechanism also acts as a positive stop for the click adjustment valve screw when it is in the fully open position.
 11. An improved adjustable gas block for a gas-operated auto-loading firearm, the firearm having a barrel with a gas port, a receiver with a forward end, and a gas cylinder with a gas inlet port, the barrel and gas cylinder joined to the receiver forward end, the gas cylinder also containing a gas piston, and the improved adjustable gas block comprising: a) a gas block housing manufactured of a suitable material with an apparatus to secure the gas block to the barrel, the gas block housing having a longitudinal bore extending through the housing to receive the firearm barrel, and having a second bore parallel to the first bore and extending a predetermined distance and adapted to receive the firearm's gas cylinder, b) the gas block housing also including a gas transfer port, further defined as aligned with both the barrel gas port and the gas cylinder inlet, which when unobstructed permits the flow of propellant gas from the barrel gas port through the gas transfer port into the gas cylinder, thus initiating the motion of the gas piston which, in turn, operates the auto-loading mechanism of the firearm, c) the gas transfer port being transversely intersected by a click adjustment valve screw with a distance of travel sufficient to render the gas transfer port either entirely open to the unhindered passage of propellant gas or entirely closed so as to completely prevent the flow of gas, d) the click adjustment valve screw further, having an area larger in diameter than the threaded body, and having evenly spaced grooves manufactured in said area parallel with the axis of the screw shank, said grooves being engaged by a spring-driven detent mechanism, being able thereby to be adjusted, either by use of a tool or a finger-manipulable knob, so as to be in a number of discrete positions between fully open and fully closed, the detent mechanism holding the click adjustment valve screw in a precise, repeatable setting.
 12. The adjustable gas block of claim 11 embodied in a front sight.
 13. The adjustable gas block of claim 11 embodied in a gas block with an integral accessory rail.
 14. The adjustable gas block of claim 11 further comprising a click adjustment valve screw with a finger-manipulable knob or handle.
 15. The adjustable gas block of claim 11 further comprising a click adjustment valve screw with a finger-manipulable knob or handle which also has a slot fitted for a coin or screwdriver.
 16. The adjustable gas block of claim 11 wherein the click adjustment valve screw has a shaped end.
 17. The adjustable gas block of claim 11 wherein the click adjustment valve screw has a squared end.
 18. The adjustable gas block of claim 11 wherein the detent element is spherical in shape.
 19. The adjustable gas block of claim 11 wherein the detent element is a pin.
 20. The adjustable gas block of claim 11 wherein a mechanism is provided to prevent the click adjustment valve screw from being inadvertently removed during use, and said mechanism also acts as a positive stop for the click adjustment valve screw when it is in the fully open position. 